1. Technical Field
The present invention relates to an apparatus and method for sealing films.
2. Description of Related Art
Various materials can be sealed using ultrasonic energy. The process typically involves vibrating a horn in close proximity to an anvil. Frictional forces in the material between the horn and the anvil provide the necessary heat for sealing.
There are many disadvantages to using ultrasonic energy to seal two films. One problem is the lap seal. In many packages made of films, the seals comprise varying numbers of layers. As an example, the seal will comprise three layers at the location of the lap seal but only two layers elsewhere. If a proper amount of energy is used for the two-layer seal, then this is insufficient energy to seal at the lap seal. Likewise, if a proper amount of energy is used at the lap seal, then too much energy is applied to the seal with only two layers resulting in an inadequate seal. Consequently, it is desirable to provide a method and apparatus which can seal films having a variable number of layers.